This invention relates to a method of producing a catalyst for converting hydrocarbons. More particularly, it relates to a method of producing a catalyst for converting hydrocarbons exhibiting outstanding effects as a fluidized catalytic cracking catalyst for producing light oils, such as gasoline or kerosene, by catalytic cracking of heavy oils containing at least nickel and vanadium, among heavy metals comprised of nickel, vanadium, iron and copper in an amount of 0.5 ppm or more as a sum total of the contents of nickel and vanadium.
In catalytic cracking in general, petroleum hydrocarbons are cracked by being contacted with a catalyst to produce a larger amount of light fractions such as LPG and gasoline and a small amount of cracked light oils, and the coke deposited on the catalyst is burned off with air for circulation and re-use of the catalyst. As starting oils, distillates such as light gas oil (LGO) or heavy gas oil (HGO) from an atmospheric distillation tower and vacuum gas oil (VGO) from a vacuum distillation tower are mainly employed.
However, since heavy oils tend to be supplied in surplus due to the world-wide tendency towards heavy crude oils and changes in the demand structure, it becomes necessary to use heavy oils containing distillation residues as the starting oil for catalytic cracking.
However, larger quantities of metals such as nickel, vanadium, iron, copper or sodium are contained in heavy oils containing distillation residues than in distillates. These metals are known to be deposited on catalysts to seriously impede cracking activity and selectivity. That is, the conversion is lowered with deposition of metals on the catalysts. On the other hand, hydrogen and coke are significantly increased to render the system operation difficult as well as to lower the yield of desirable liquid products.
For diminishing the effects of these pollutant metals, there have hitherto been proposed a method of employing a catalyst containing a metal trap or a method of physically mixing discrete particles containing a metal trap with a cracking catalyst. Compounds of alkaline earth elements are known to be effective as the metal trap. For example, Japanese Laid-open Patent Application No.1-146989 discloses using oxides of alkaline earth metals carried by silica. Japanese Laid-open Patent Applications Nos.63-8481, 62-213843 and 61-21191 disclose using magnesium compounds, whereas Japanese Laid-open Patent Application Nos.61-204041 and 60-71041 disclose using calcium compounds. Although the compounds of alkaline earth metals are effective as a metal trap, these compounds are disadvantageous in that they are adsorbed on zeolite which is an active component in the catalyst to lower the hydrothermal stability of the catalyst. On the other hand, silica sol or alumina sol used as a material of catast binder is stable only in an acidic solution so that upon preparation of a catalyst, the addition of basic alkaline earth compounds to a sol-containing slurry results in gelation of the binder before spray-drying to lower the attrition resistance of the catalyst. For overcoming these drawbacks, the catalysts containing the compounds of alkaline earth metals as the metal trap are used as physical mixtures of diluent particles containing the metal trap and particles of the cracking catalysts containing zeolite. However, for diminishing the effects of pollutant metals, it is more effective that the metal trap and zeolite be contained in one and the same particle. Japanese Laid-open Patent Application Nos.61-278351 and 63-123804, for example disclose building zeolite and the magnesium compounds as the metal trap in one and the same particle. However, in the conventional catalysts containing the magnesium compounds and zeolite in one and the same particle, the adverse effects which the magnesium compound might have on zeolite have not been studied with satisfactory results.